Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation by drilling a well that penetrates the hydrocarbon-bearing formation. This provides a partial flowpath for the hydrocarbon to reach the surface. The hydrocarbon is “produced,” or travels from the formation to the wellbore (and ultimately to the surface), via a sufficiently unimpeded flowpath from the formation to the wellbore.
Hydraulic fracturing is a tool for improving well productivity by placing or extending channels from the wellbore to the formation. This operation comprises hydraulically injecting a fracturing fluid into a wellbore penetrating a subterranean formation, thus forcing the fracturing fluid against the formation strata by pressure. The formation strata or rock is thus forced to crack and fracture. Proppant may then be placed in the fracture to prevent the fracture from closing.
Oftentimes, a single wellbore will have multiple zones to be fractured. Once the casing hardware is cemented in place, stimulating applications generally take place in a zone by zone fashion. One conventional method for fracturing multiple zones involves a bottom-up approach where a lowermost zone is fractured first, and zones closer to the surface are subsequently fractured. For example, a terminal end of the well may be perforated and fractured followed by setting of a plug immediately uphole thereof. Thus, with the lowermost zone initially stimulated, the zone above the plug may now also be stimulated by way of repeating the perforating and fracturing applications. This time consuming sequence of plug setting, perforating and then fracturing is repeated for each zone.
There are many situations when one would like to selectively activate multiple downhole devices. For example, in typical wellbore operations, various treatment fluids may be pumped into the well and eventually into the formation to restore or enhance the productivity of the well. For example, a non-reactive fracturing fluid may be pumped into the wellbore to initiate and propagate fractures in the formation thus providing flow channels to facilitate movement of the hydrocarbons to the wellbore so that the hydrocarbons may be pumped from the well.
In such fracturing operations, the fracturing fluid is hydraulically injected into a wellbore penetrating the subterranean formation and is forced against the formation strata by pressure. The formation strata is forced to crack and fracture, and a proppant is placed in the fracture by movement of a viscous-fluid containing proppant into the crack in the rock. The resulting fracture, with proppant in place, provides improved flow of the recoverable fluid (i.e. oil, gas or water) into the wellbore. Often it is desirable to have multiple production zones which are treated differently within the wellbore. To isolate and treat each zone separately, previous mechanisms have been time consuming and expensive among other drawbacks.
Due to the heterogeneous nature of formation, one might not want to open all the valves simultaneously so that the fracturing operations can be performed separately for different layers of formation.